1. Field of the Invention
The present invention relates to a gasket seals for a sliding rod passing through a guide bushing and, more particularly, to small-size gaskets such as, inter alia, the gasket seals between valve rods and guides in internal combustion engines.
2. Description of the Prior Art
Known gasket seals between a valve rod and guide are generally constructed from plastic material and consist of two serial, coaxial, staged, rotating sections, with one fitting over the end of the valve guide and the second, of smaller diameter, forming a sliding seal for the valve rod, the two being joined together by a simple shoulder. This shape, given the small size of the gasket seal, makes the latter too rigid and does not enable it to effectively absorb any defects of concentricity which may exist between the outer diameter of the valve guide and its bore, in which the valve rod moves. These defects of concentricity thus result in abnormal wear of the gasket seal, wear which quickly becomes harmful to the sealing effect sought.
It is current practice in manufacturing to perform on the cylinder heads of internal combustion engines a reboring of the valve guides for the purpose of aligning their bore with the corresponding valve bearings on the valve seat. From this, there frequently results slight defects in concentricity between the bore and the outer diameter of the valve guides.